This invention relates to the field of oscillating spouts. More particularly, this invention relates to an apparatus and process for controlling the movement of an oscillating spout capable of pivoting about two orthogonal axes, the spout being actuated by two independent driving means in order to move the end of the spout over concentric circles or over a spiral course around a vertical axis.
The method and apparatus of the present invention are well suited for use in conjunction with a charging installation of a shaft furnace. A shaft furnace charging apparatus employing an oscillating distributing spout is disclosed in Luxembourg Patent Application No. 83,280 corresponding to U.S. patent application Ser. Nos. 288,974 and 675,301, now U.S. Pat. Nos. 4,525,120 and 4,547,116, respectively, which are both assigned to the assignee herein and is of the general type to which the present invention is directed. That charging apparatus is generally known in the art as a spout with a cardan-type suspension.
Experiments on a conventional charging device of the type hereinabove described reveal that the layers of material deposited by means of an oscillating spout within the shaft furnace are of uneven thickness. Obviously, if only a single layer of material was utilized, these irregularities in thickness would have no especially damaging effects upon the charging of a shaft furnace. Unfortunately, these irregularities are repeated at the same points for each layer deposited. These points of irregular distribution correspond to certain angular positions of the spout. Thus, the respective uneven layers exhibit a cumulative effect which result in a saddle-shaped charging level. It has also been found that this defect is not peculiar to the apparatus disclosed in the aformentioned Luxembourg patent application; rather, it occurs to a greater or lesser extent in all charging apparatus having a spout suspension system of the cardan-type, regardless of the particular driving and control means used.
The uneven charging thickness occurs because cardan-type distributing spouts undergo slight but nevertheless perceptible pivoting movements about their longitudinal axis at certain diametrically opposed points in the course of each revolution. When this pivoting movement starts, there is a reduction in friction effects between the charge material and the spout and also within the charge material, as the charge passes through the spout. Thus, the speed of fall of the material increases. In other words, the onset of the pivoting movement causes the material to reach its fall or impact point more quickly; and the thickness of the deposited layer increases in the places where the fall or impact point occurs corresponding to the angular position which the spout occupies when the pivoting movement takes place. Similarly, the opposite effect is produced at the end of the pivoting movement of the spout, i.e., the friction effects within the spout once again increases, thus leading to a reduction in the thickness of the layer deposited at the corresponding fall or impact point of the material.